The resistance of a wire depends on certain factors. Some of these variables are listed below: Length of wire Diameter of wire Temperature at which wire is at

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Introduction

Resistance of wires

Aims

To investigate how increasing and decreasing the thickness and length of a wire affects its resistance.

Background Knowledge

Resistance

An electron travelling through the wires and loads of the external circuit encounters resistance. Resistance is the hindrance to the flow of charge. For an electron, the journey from terminal to terminal is not a direct route. Rather, it is a zigzag path, which results from countless collisions with fixed atoms within the conducting material. The electrons encounter resistance - a hindrance to their movement. While the electric potential difference established between the two terminals encourages the movement of charge, it is resistance that discourages it. The rate at which charge flows from terminal to terminal is the result of the combined effect of these two quantities.

Resistance is measured in ohms and can be calculated by using the formula R = V/I.

Possible Variables

The resistance of a wire depends on certain factors. Some of these variables are listed below:

The larger the length of the wire, the larger the resistance. This is because there are more atoms from the metal so there is more chance that the electrons would collide with one of the atoms therefore there is more resistance. The length of wire will be variable throughout the investigation. Electrons have a longer distance to travel when the wire is longer, so there are more collisions .The length of the wire will make a difference to the resistance. This is because when you have a long wire, the electrons have to squeeze together for longer to be able to pass through the wire than they do in order to be able to pass through a short wire.

3) Type of material l Different materials have different resistances because the materials' atomic structures are different so some metals have low resistances and some have high resistances. Therefore it is important to keep the material the same throughout the experiment unless a different material is used to check if the conclusion or theory works for all materials. If different materials are used throughout the investigation, it will affect the results.

I predict that if the length increases then the resistance will also increase in proportional to the length.

I think this because, as I have explained above in my background knowledge, the longer the wire the more atoms and so the more likely the electrons are going to collide with the atoms. If I had a 30 cm wire and a 60 cm wire, the 60 cm wire would have a resistance twice that of the 30 cm wire. Therefore, if the length is doubled the resistance should also double. This is because if the length is doubled the number of atoms will also double resulting in twice the number of collisions slowing the electrons down and increasing the resistance. My graph should show that the Length is directly proportional to the resistance.If the length of the wire is only half the length of the wire on the same type of wire, there should be half the number of collisions between the electrons and the atoms.If the wire is twice as long, there should be twice the number of atoms, resulting in twice as many collisions and a predicted doubling of the resistance.

Related GCSE Electricity and Magnetism essays

measure the thickness of the wire at intervals using a micrometer screw gauge. I will also try to use the same equipment for each current because any change of equipment that might cause a distortion of results. To make it a fair test, only one factor should be altered at a time.

the one that gives the biggest readings on the meter scale without overloading the scale. Also before starting the experiment the multi ammeter and multi voltmeter must be checked to read zero before use to ensure they read zero when disconnected or this will affect the final result.

As they move faster through the wire, there are collisions between the electrons and the positively charged ions of the wire and when the fast flowing electrons collide with the ions, it causes resistance. We can also predict this in a microscopic view.

to make sure your results are correct you could try it again to get an average reading. This enables you to view whether the results are strong evidence to my hypothesis. When I measured the wires at the lowest distance of 10cm I discovered that there was less difference between the wires than at the furthest distance of 100cm.

not be completely straight, it may be of different thickness throughout the length. These would have contributed as well to the error. There was one slightly anomalous result, at 0.25mm2. This could have been due to a unique error in the measuring and or reading of the meters, or a temperature change.

Ohm's Law = I ? V Not all electrical components will obey Ohm's Law. The most obvious example of one that does not is a filament lamp, whose resistance will increase as the voltage increases because its voltage and current are not directly proportional.

Method: Using the circuit I have designed I will be able to test the different lengths of wire that I am using, simply by clipping them into this space. My circuit has been designed in order to make the change from one length of wire to another quick and simple.